It's not really ground breaking or anything, but was a fun little project to get better with python and pyqt. All of the source code and a standalone windows installer are posted on my site, so feel free to use and/or modify it.
Basically it does the exact same thing as the serial monitor in the Arduino IDE, but will also save all of the read in data to file. If the data is of a certain format (CSV with the first column being time in ms), you can also plot slower data in real time. Much faster than 1 or 2 Hz leads to alot of lag. Pun intended. Any plotted data can be saved as an image, or FFT-ed pretty easily, as an added little bonus.